fix(ui): restore StarMap node in hud.tscn

Accidentally deleted when exploring reparenting options. The z-index
model means it stays as a child of HUD — no reparenting needed.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

client/ui/hud.tscn

@@ -38,6 +38,7 @@ text = "Mode: Baseline"
 layout_mode = 2
 text = "Time: 08:00"
 
-; #674: Star map insert — concentric hop-ring view, hidden by default, toggled via keybind
+; #674: Star map insert — D-170 z-index layer managed, not visibility toggled
 [node name="StarMap" parent="." instance=ExtResource("2_starmap")]
 visible = false
+